User initiated break-away clutching of a surgical mounting platform

ABSTRACT

Robotic and/or surgical devices, systems, and methods include kinematic linkage structures and associated control systems configured to facilitate preparation of the system for use. One or more kinematic linkage sub-systems may include joints that are actively driven, passive, or a mix of both. A set-up mode employs an intuitive user interface in which one or more joints are initially held static by a brake or joint drive system. The user may articulate the joint(s) by manually pushing against the linkage with a force, torque, or the like that exceeds a manual articulation threshold. Articulation of the moving joints is facilitated by modifying the signals transmitted to the brake or drive system. The system may sense completion of the reconfiguration from a velocity of the joint(s) falling below a threshold, optionally for a desired dwell time. The system may provide a detent-like manual articulation that is not limited to mechanically pre-defined detent joint configurations. Embodiments of the invention provide, and can be particularly well-suited for manual movement of a platform supporting a plurality of surgical manipulators in a robotic surgical system or the like without having to add additional input devices.

BACKGROUND

Minimally invasive medical techniques are intended to reduce the amount of extraneous tissue that is damaged during diagnostic or surgical procedures, thereby reducing patient recovery time, discomfort, and deleterious side effects. One effect of minimally invasive surgery, for example, is reduced post-operative hospital recovery times. Because the average hospital stay for a standard surgery is typically significantly longer than the average stay for an analogous minimally invasive surgery, increased use of minimally invasive techniques could save millions of dollars in hospital costs each year. While many of the surgeries performed each year in the United States could potentially be performed in a minimally invasive manner, only a portion of the current surgeries use these advantageous techniques due to limitations in minimally invasive surgical instruments and the additional surgical training involved in mastering them.

Minimally invasive robotic surgical or telesurgical systems have been developed to increase a surgeon's dexterity and avoid some of the limitations on traditional minimally invasive techniques. In telesurgery, the surgeon uses some form of remote control (e.g., a servomechanism or the like) to manipulate surgical instrument movements, rather than directly holding and moving the instruments by hand. In telesurgery systems, the surgeon can be provided with an image of the surgical site at a surgical workstation. While viewing a two or three dimensional image of the surgical site on a display, the surgeon performs the surgical procedures on the patient by manipulating master control devices, which in turn control motion of the servo-mechanically operated instruments.

The servomechanism used for telesurgery will often accept input from two master controllers (one for each of the surgeon's hands) and may include two or more robotic arms on each of which a surgical instrument is mounted. Operative communication between master controllers and associated robotic arm and instrument assemblies is typically achieved through a control system. The control system typically includes at least one processor that relays input commands from the master controllers to the associated robotic arm and instrument assemblies and back from the instrument and arm assemblies to the associated master controllers in the case of, for example, force feedback or the like. One example of a robotic surgical system is the DA VINCI® system available from Intuitive Surgical, Inc. of Sunnyvale, Calif.

A variety of structural arrangements can be used to support the surgical instrument at the surgical site during robotic surgery. The driven linkage or “slave” is often called a robotic surgical manipulator, and exemplary linkage arrangements for use as a robotic surgical manipulator during minimally invasive robotic surgery are described in U.S. Pat. Nos. 7,594,912; 6,758,843; 6,246,200; and 5,800,423; the full disclosures of which are incorporated herein by reference. These linkages often make use of a parallelogram arrangement to hold an instrument having a shaft. Such a manipulator structure can constrain movement of the instrument so that the instrument pivots about a remote center of manipulation positioned in space along the length of the rigid shaft. By aligning the remote center of manipulation with the incision point to the internal surgical site (for example, with a trocar or cannula at an abdominal wall during laparoscopic surgery), an end effector of the surgical instrument can be positioned safely by moving the proximal end of the shaft using the manipulator linkage without imposing potentially dangerous forces against the abdominal wall. Alternative manipulator structures are described, for example, in U.S. Pat. Nos. 7,763,015; 6,702,805; 6,676,669; 5,855,583; 5,808,665; 5,445,166; and 5,184,601; the full disclosures of which are incorporated herein by reference.

A variety of structural arrangements can also be used to support and position the robotic surgical manipulator and the surgical instrument at the surgical site during robotic surgery. Supporting linkage mechanisms, sometimes referred to as set-up joints, or set-up joint arms, are often used to position and align each manipulator with the respective incision point in a patient's body. The supporting linkage mechanism facilitates the alignment of a surgical manipulator with a desired surgical incision point and targeted anatomy. Exemplary supporting linkage mechanisms are described in U.S. Pat. Nos. 6,246,200 and 6,788,018, the full disclosures of which are incorporated herein by reference.

While the new telesurgical systems and devices have proven highly effective and advantageous, still further improvements are desirable. In general, improved minimally invasive robotic surgery systems are desirable. It would be particularly beneficial if these improved technologies enhanced the efficiency and ease of use of robotic surgical systems. For example, it would be particularly beneficial to increase maneuverability, improve space utilization in an operating room, provide a faster and easier set-up, inhibit collisions between robotic devices during use, and/or reduce the mechanical complexity and size of these new surgical systems.

BRIEF SUMMARY

The following presents a simplified summary of some embodiments of the invention in order to provide a basic understanding of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some embodiments of the invention in a simplified form as a prelude to the more detailed description that is presented later.

The present invention generally provides improved robotic and/or surgical devices, systems, and methods. Kinematic linkage structures and associated control systems described herein are particularly beneficial in helping system users to arrange the robotic structure in preparation for use, including in preparation for a surgical procedure on a particular patient. Exemplary robotic surgical systems described herein may have one or more kinematic linkage sub-systems that are configured to help align a manipulator structure with the surgical work site. The joints of these set-up systems may be actively driven, passive (so that they are manually articulated and then locked into the desired configuration while the manipulator is used therapeutically), or a mix of both. Embodiments of the robotic systems described herein may employ a set-up mode in which one or more joints are initially held static by a brake or joint drive system. Inadvertent articulation is limited by the brake or drive system, but the user can manually articulate the joint(s) by manually pushing against the linkage with a force, torque, or the like that exceeds a manual articulation threshold of the joint(s). Once the joint(s) begin to move, a processor may facilitate articulation with less user effort by modifying the signals transmitted to the brake or drive system. When the user arrives at a desired configuration, the system may sense that the user has completed the reconfiguration from a velocity of the joint(s) below a threshold, optionally for a desired dwell time. The system may then again inhibit inadvertent articulation of the joint(s. The dwell time can help avoid locking the linkage when reversing directions, and the system can provide a “detent” like manual articulation that is not limited to mechanically pre-defined detent joint configurations. Embodiments of the invention provide a user interface is intuitive, and can be particularly well-suited for manual movement of a platform supporting a plurality of surgical manipulators in a robotic surgical system or the like without having to add additional input devices.

In a first aspect, the invention provides a method for configuring a robotic system. The method comprises inhibiting manual articulation of a linkage of the system from a first pose in response to a first manual effort against the linkage being below a desired articulation threshold. A manual movement of the linkage from the first pose toward a second pose is facilitated in response to a second manual effort to articulate the linkage exceeding the desired articulation threshold. The second pose is determined in response to the manual movement of the linkage. Manual movement of the linkage from the second pose is inhibited.

Thus, in a first aspect, a method for configuring a robotic system is provided. The method includes inhibiting manual articulation of a linkage of the system from a first pose in response to a first manual effort against the linkage, facilitating a manual movement of the linkage from the first pose toward a second pose, determining the second pose in response to the manual movement of the linkage, and inhibiting manual movement of the linkage from the second pose. The inhibiting step is in response to a first manual effort against the linkage that is below a desired articulation threshold. The facilitating step is in response to a second manual effort against the linkage that exceeds the desired articulation threshold.

In other exemplary embodiments, a joint sensor may sense a first torque of the first manual effort applied to a joint and a processor may inhibit the manual articulation by determining drive signals configured to induce a counteracting torque to the linkage opposing the first torque so as to urge the linkage back toward the first pose. In further embodiments, the joint sensor may also sense the second torque of the second manual effort applied to the joint and the processor may be configured to determine that the second effort exceeds the desired articulation threshold. For example, in some embodiments the articulation threshold may be a torque threshold and the processor may determine that the second effort exceeds the desired articulation threshold by determining that the second torque exceeds the threshold torque. In response to a second effort exceeding the desired articulation threshold, the processor may alter the drive signals so as to decrease the counteracting torque so that the first torque is sufficient to manually move the manipulator.

In some embodiments of the method, a processor may alter drive signals in response to the second effort exceeding the desired articulation threshold by adding a friction compensation component to the drive signals so as to mitigate friction of the linkage for the manual movement toward the second pose.

In other embodiments, the second pose may be determined by determining that a velocity of the manual movement is below a threshold velocity. Additionally, the second pose may also be determined by determining that the velocity of the manual movement remains below the threshold velocity for a threshold dwell time so as to facilitate reversing a direction of the movement without inhibiting manual movement.

In further embodiments, the method for configuring a robotic system includes driving the linkage in the second pose with drive signals so as to inhibit manual movement of the linkage from the second pose in response to a third manual effort against the manipulator being below the desired articulation threshold.

The above exemplary methods may be used to configure a surgical robotic system. For example, the linkage may be a set-up structure having a proximal base and a platform with the joint disposed therebetween. The platform may support a plurality of surgical manipulators, where each manipulator may be an instrument holder configured to releasably receive a surgical instrument. The manual movement may be a movement that alters positions of the plurality of manipulators relative to a surgical site. In another example, the linkage may be included in a surgical manipulator having a holder for releasably receiving a surgical instrument. The surgical manipulator may also include a cannula interface configured for releasably receiving a cannula. The manipulator may be further configured to pivotably move a shaft of the instrument within an aperture adjacent the cannula so as to manipulate an end effector of the instrument within a minimally invasive surgical aperture. The configuration method may further include inhibiting manual articulation of the joint with manual effort exceeding the desired articulation threshold in response to the mounting of the cannula to the cannula interface.

In another aspect, a robotic system is provided. The robotic system includes a linkage having a joint, a drive or brake system coupled to the linkage, and a processor coupled with the drive or brake system. The processor may be configured to transmit signals to the drive or brake system so as to inhibit manual articulation of the linkage from a first pose in response to a first manual effort against the linkage being below a desired articulation threshold. The processor may alter the signals in response to a second manual effort to articulate the linkage exceeding the desired articulation threshold. The altered signals may be configured to facilitate a manual movement of the linkage from the first pose toward a second pose. The processor may also determine the second pose in response to the manual movement of the linkage and may transmit the signals to the drive system so as to inhibit manual movement of the linkage from the second pose.

In additional exemplary embodiments, the robotic system further includes a joint sensor coupled to the joint. The joint sensor may be configured to sense a first torque of the first manual effort applied to the joint. The processor may be configured to determine the signals so as to apply a counteracting torque to the linkage opposing the first torque and urge the linkage back toward the first pose. In particular embodiments, a drive or brake system may include a drive system. Further, the joint sensor may be configured so as to transmit to the processor a second torque of the second manual effort applied to the joint. The processor may be further configured to determine if the second effort exceeds the desired articulation threshold using the second torque. For example, the processor may be configured to determine that the second effort exceeds the desired articulation threshold by determining whether the second torque exceeds a threshold torque. In response to a second effort exceeding the desired articulation threshold, the processor may alter the drive signals so as to decrease the counteracting torque so that the first torque is sufficient to manually move the manipulator.

In some embodiments, the signals of the robotic system may include drive signals and the processor may be configured to alter the drive signals in response to the second effort exceeding the desired articulation threshold by adding a friction compensation component to the drive signals so as to mitigate friction of the linkage for the manual movement toward the second pose.

The processor may be configured to determine a second pose in response to a velocity of the manual movement being below a threshold velocity. The processor may be further configured to determine the second pose by determining that the velocity of the manual movement is below the threshold velocity for a threshold dwell time so as to facilitate a reversal of a direction of the manual movement without inhibiting the manual movement. The processor may also be configured to inhibit manual movement of the linkage from the second pose in response to a third manual effort against the manipulator being below the desired articulation threshold.

The above exemplary system may be a surgical robotic system. For example, the linkage may be a set-up structure having a proximal base and a platform with the joint disposed therebetween. The platform may support a plurality of surgical manipulators, where each manipulator may be an instrument holder configured to releasably receive a surgical instrument. The manual movement may be a movement that alters positions of the plurality of manipulators relative to a surgical site. In another example, the linkage may be included in a surgical manipulator having a holder for releasably receiving a surgical instrument. The surgical manipulator may also include a cannula interface configured for releasably receiving a cannula. The manipulator may be further configured to pivotably move a shaft of the instrument within an aperture adjacent the cannula so as to manipulate an end effector of the instrument within a minimally invasive surgical aperture. The system may further include inhibiting manual articulation of the joint with manual effort exceeding the desired articulation threshold in response to the mounting of the cannula to the cannula interface.

In an additional aspect, a robotic surgical system is provided. The robotic surgical system includes a linkage having a joint, a drive system coupled to the linkage, a torque sensor system coupled to the joint, and a processor coupling the torque sensor with the drive system. The joint may be disposed between a proximal base and an instrument holder. The instrument holder may be configured for releasably supporting a surgical instrument. The processor is configured to transmit drive signals to the drive system so as to inhibit manual articulation of the joint from a first configuration in response to a sensed torque being below a desired articulation threshold. In response to a sensed torque exceeding the desired articulation threshold, the processor may alter the drive signals to facilitate a manual movement of the joint from the first configuration toward a second configuration using a movement torque lower than the articulation threshold. In response to a velocity of the manual movement being below a threshold velocity, the processor may determine the second configuration. The processor may also be configured to transmit drive signals to the drive system so as to inhibit manual movement of the linkage from the second pose in response to a sensed torque being below a desired articulation threshold.

In another aspect, a method of configuring a robotic system is provided. The method includes driving a robotic assembly during manual efforts to move a linkage of the assembly so as to simulate a first and second detent of the linkage at first and second linkage poses. The method also includes determining the second pose in response to a manual movement of the linkage to the second pose.

For a fuller understanding of the nature and advantages of the present invention, reference should be made to the ensuing detailed description and accompanying drawings. Other aspects, objects and advantages of the invention will be apparent from the drawings and detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a minimally invasive robotic surgery system being used to perform a surgery, in accordance with many embodiments.

FIG. 2 is a perspective view of a surgeon's control console for a robotic surgery system, in accordance with many embodiments.

FIG. 3 is a perspective view of a robotic surgery system electronics cart, in accordance with many embodiments.

FIG. 4 diagrammatically illustrates a robotic surgery system, in accordance with many embodiments.

FIG. 5A is a partial view of a patient side cart (surgical robot) of a robotic surgery system, in accordance with many embodiments.

FIG. 5B is a front view of a robotic surgery tool, in accordance with many embodiments.

FIG. 6 is a perspective schematic representation of a robotic surgery system, in accordance with many embodiments.

FIG. 7 is a perspective schematic representation of another robotic surgery system, in accordance with many embodiments.

FIG. 8 shows a robotic surgery system, in accordance with many embodiments, in conformance with the schematic representation of FIG. 7.

FIG. 9 illustrates rotational orientation limits of set-up linkages relative to an orienting platform of the robotic surgery system of FIG. 8.

FIG. 10 shows a center of gravity diagram associated with a rotational limit of the boom assembly for a robotic surgery system, in accordance with many embodiments.

FIG. 11 is a flow chart schematically illustrating a method for preparing a robotic surgical system for surgery.

DETAILED DESCRIPTION

In the following description, various embodiments of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described.

The kinematic linkage structures and control systems described herein are particularly beneficial in helping system users to arrange the robotic structure of a procedure on a particular patient. Along with actively driven manipulators used to interact with tissues and the like during treatment, robotic surgical systems may have one or more kinematic linkage systems that are configured to support and help align the manipulator structure with the surgical work site. These set-up systems may be actively driven or may be passive, so that they are manually articulated and then locked into the desired configuration while the manipulator is used therapeutically. The passive set-up kinematic systems may have advantages in size, weight, complexity, and cost. Unfortunately, a plurality of manipulators may be used to treat tissues of each patient, the manipulators may each independently benefit from accurate positioning so as to allow the instrument supported by that instrument to have the desired motion throughout the workspace, and minor changes in the relative locations of adjacent manipulators may have significant impact on the interactions between manipulators (with poorly positioned manipulators potentially colliding or having their range and/or ease of motion significantly reduced). Hence, the challenges of quickly arranging the robotic system in preparation for surgery can be significant.

One option is to mount multiple manipulators to a single platform, with the manipulator-supporting platform sometimes being referred to as an orienting platform. The orienting platform can be supported by an actively driven support linkage (sometimes referred to herein as a set-up structure, and typically having a set-up structure linkage, etc.) The system may also provide and control motorized axes of the robotic set-up structure supporting the orienting platform with some kind of joystick or set of buttons that would allow the user to actively drive those axes as desired in an independent fashion. This approach, while useful in some situations, may suffer from some disadvantages. In particular, it may be difficult to locate a drive button for all the elements of a complex system so that each is accessible to users approaching the system in all its potential configurations. While individual clutch buttons might also be used to release the brake or drive system, the possibility of confusion may remain between buttons having different functions. Furthermore, both sterile and non-sterile members of a surgical team may want to articulate some joints or linkages (such as by grabbing differing locations inside or outside the sterile field). Hence a more intuitive and flexible user interface would be desirable. This is particularly true of an orienting platform for use in multi-quadrant surgery, or for a structure that supports a plurality of surgical manipulators and may pivot about an axis extending at least roughly vertically so as to orient the manipulators relative to a patient on a surgical table or other support.

Minimally Invasive Robotic Surgery

Referring now to the drawings, in which like reference numerals represent like parts throughout the several views, FIG. 1 is a plan view illustration of a Minimally Invasive Robotic Surgical (MIRS) system 10, typically used for performing a minimally invasive diagnostic or surgical procedure on a Patient 12 who is lying down on an Operating table 14. The system can include a Surgeon's Console 16 for use by a Surgeon 18 during the procedure. One or more Assistants 20 may also participate in the procedure. The MIRS system 10 can further include a Patient Side Cart 22 (surgical robot) and an Electronics Cart 24. The Patient Side Cart 22 can manipulate at least one removably coupled tool assembly 26 (hereinafter simply referred to as a “tool”) through a minimally invasive incision in the body of the Patient 12 while the Surgeon 18 views the surgical site through the Console 16. An image of the surgical site can be obtained by an endoscope 28, such as a stereoscopic endoscope, which can be manipulated by the Patient Side Cart 22 to orient the endoscope 28. The Electronics Cart 24 can be used to process the images of the surgical site for subsequent display to the Surgeon 18 through the Surgeon's Console 16. The number of surgical tools 26 used at one time will generally depend on the diagnostic or surgical procedure and the space constraints within the operating room among other factors. If it is necessary to change one or more of the tools 26 being used during a procedure, an Assistant 20 may remove the tool 26 from the Patient Side Cart 22, and replace it with another tool 26 from a tray 30 in the operating room.

FIG. 2 is a perspective view of the Surgeon's Console 16. The Surgeon's Console 16 includes a left eye display 32 and a right eye display 34 for presenting the Surgeon 18 with a coordinated stereo view of the surgical site that enables depth perception. The Console 16 further includes one or more input control devices 36, which in turn cause the Patient Side Cart 22 (shown in FIG. 1) to manipulate one or more tools. The input control devices 36 can provide the same degrees of freedom as their associated tools 26 (shown in FIG. 1) to provide the Surgeon with telepresence, or the perception that the input control devices 36 are integral with the tools 26 so that the Surgeon has a strong sense of directly controlling the tools 26. To, this end, position, force, and tactile feedback sensors (not shown) may be employed to transmit position, force, and tactile sensations from the tools 26 back to the Surgeon's hands through the input control devices 36.

The Surgeon's Console 16 is usually located in the same room as the patient so that the Surgeon may directly monitor the procedure, be physically present if necessary, and speak to an Assistant directly rather than over the telephone or other communication medium. However, the Surgeon can be located in a different room, a completely different building, or other remote location from the Patient allowing for remote surgical procedures.

FIG. 3 is a perspective view of the Electronics Cart 24. The Electronics Cart 24 can be coupled with the endoscope 28 and can include a processor to process captured images for subsequent display, such as to a Surgeon on the Surgeon's Console, or on another suitable display located locally and/or remotely. For example, where a stereoscopic endoscope is used, the Electronics Cart 24 can process the captured images to present the Surgeon with coordinated stereo images of the surgical site. Such coordination can include alignment between the opposing images and can include adjusting the stereo working distance of the stereoscopic endoscope. As another example, image processing can include the use of previously determined camera calibration parameters to compensate for imaging errors of the image capture device, such as optical aberrations.

FIG. 4 diagrammatically illustrates a robotic surgery system 50 (such as MIRS system 10 of FIG. 1). As discussed above, a Surgeon's Console 52 (such as Surgeon's Console 16 in FIG. 1) can be used by a Surgeon to control a Patient Side Cart (Surgical Robot) 54 (such as Patient Side Cart 22 in FIG. 1) during a minimally invasive procedure. The Patient Side Cart 54 can use an imaging device, such as a stereoscopic endoscope, to capture images of the procedure site and output the captured images to an Electronics Cart 56 (such as the Electronics Cart 24 in FIG. 1). As discussed above, the Electronics Cart 56 can process the captured images in a variety of ways prior to any subsequent display. For example, the Electronics Cart 56 can overlay the captured images with a virtual control interface prior to displaying the combined images to the Surgeon via the Surgeon's Console 52. The Patient Side Cart 54 can output the captured images for processing outside the Electronics Cart 56. For example, the Patient Side Cart 54 can output the captured images to a processor 58, which can be used to process the captured images. The images can also be processed by a combination the Electronics Cart 56 and the processor 58, which can be coupled together to process the captured images jointly, sequentially, and/or combinations thereof. One or more separate displays 60 can also be coupled with the processor 58 and/or the Electronics Cart 56 for local and/or remote display of images, such as images of the procedure site, or other related images.

Processor 58 will typically include a combination of hardware and software, with the software comprising tangible media embodying computer readable code instructions for performing the method steps of the control functionally described herein. The hardware typically includes one or more data processing boards, which may be co-located but will often have components distributed among the robotic structures described herein. The software will often comprise a non-volatile media, and could also comprise a monolithic code but will more typically comprise a number of subroutines, optionally running in any of a wide variety of distributed data processing architectures.

FIGS. 5A and 5B show a Patient Side Cart 22 and a surgical tool 62, respectively. The surgical tool 62 is an example of the surgical tools 26. The Patient Side Cart 22 shown provides for the manipulation of three surgical tools 26 and an imaging device 28, such as a stereoscopic endoscope used for the capture of images of the site of the procedure. Manipulation is provided by robotic mechanisms having a number of robotic joints. The imaging device 28 and the surgical tools 26 can be positioned and manipulated through incisions in the patient so that a kinematic remote center is maintained at the incision to minimize the size of the incision. Images of the surgical site can include images of the distal ends of the surgical tools 26 when they are positioned within the field-of-view of the imaging device 28.

Surgical tools 26 are inserted into the patient by inserting a tubular cannula 64 through a minimally invasive access aperture such as an incision, natural orifice, percutaneous penetration, or the like. Cannula 64 is mounted to the robotic manipulator arm and the shaft of surgical tool 26 passes through the lumen of the cannula. The manipulator arm may transmit signals indicating that the cannula has been mounted thereon.

Robotic Surgery Systems and Modular Manipulator Supports

FIG. 6 is a perspective schematic representation of a robotic surgery system 70, in accordance with many embodiments. The surgery system 70 includes a mounting base 72, a support linkage 74, an orienting platform 76, a plurality of outer set-up linkages 78 (two shown), a plurality of inner set-up linkages 80 (two shown), and a plurality of surgical instrument manipulators 82. Each of the manipulators 82 is operable to selectively articulate a surgical instrument mounted to the manipulator 82 and insertable into a patient along an insertion axis. Each of the manipulators 82 is attached to and supported by one of the set-up linkages 78, 80. Each of the outer set-up linkages 78 is rotationally coupled to and supported by the orienting platform 76 by a first set-up linkage joint 84. Each of the inner set-up linkages 80 is fixedly attached to and supported by the orienting platform 76. The orienting platform 76 is rotationally coupled to and supported by the support linkage 74. And the support linkage 74 is fixedly attached to and supported by the mounting base 72.

In many embodiments, the mounting base 72 is a movable and floor supported, thereby enabling selective repositioning of the overall surgery system 70, for example, within an operating room. The mounting base 72 can include a steerable wheel assembly and/or any other suitable support features that provide for both selective repositioning as well as selectively preventing movement of the mounting base 72 from a selected position. The mounting base 72 can also have other suitable configurations, for example, a ceiling mount, fixed floor/pedestal mount, a wall mount, or an interface configured for being supported by any other suitable mounting surface.

The support linkage 74 is operable to selectively position and/or orient the orienting platform 76 relative to the mounting base 72. The support linkage 74 includes a column base 86, a translatable column member 88, a shoulder joint 90, a boom base member 92, a boom first stage member 94, a boom second stage member 96, and a wrist joint 98. The column base 86 is fixedly attached to the mounting base 72. The translatable column member 88 is slideably coupled to the column base 86 for translation relative to column base 86. In many embodiments, the translatable column member 88 translates relative to the column base 86 along a vertically oriented axis. The boom base member 92 is rotationally coupled to the translatable column member 88 by the shoulder joint 90. The shoulder joint 90 is operable to selectively orient the boom base member 92 in a horizontal plane relative to the translatable column member 88, which has a fixed angular orientation relative to the column base 86 and the mounting base 72. The boom first stage member 94 is selectively translatable relative to the boom base member 92 in a horizontal direction, which in many embodiments is aligned with both the boom base member 92 and the boom first stage member 94. The boom second stage member 96 is likewise selectively translatable relative to the boom first stage member 94 in a horizontal direction, which in many embodiments is aligned with the boom first stage member 94 and the boom second stage member 96. Accordingly, the support linkage 74 is operable to selectively set the distance between the shoulder joint 90 and the distal end of the boom second stage member 96. The wrist joint 98 rotationally couples the distal end of the boom second stage member 96 to the orienting platform 76. The wrist joint 98 is operable to selectively set the angular orientation of the orienting platform 76 relative to the mounting base 72.

Each of the set-up linkages 78, 80 is operable to selectively position and/or orient the associated manipulator 82 relative to the orienting platform 76. Each of the set-up linkages 78, 80 includes a set-up linkage base link 100, a set-up linkage extension link 102, a set-up linkage parallelogram linkage portion 104, a set-up linkage vertical link 106, a second set-up linkage joint 108, and a manipulator support link 110. In each of the set-up linkage base links 100 of the outer set-up linkages 78 can be selectively oriented relative to the orienting platform 76 via the operation of the a first set-up linkage joint 84. In the embodiment shown, each of the set-up linkage base links 100 of the inner set-up linkages 80 is fixedly attached to the orienting platform 76. Each of the inner set-up linkages 80 can also be rotationally attached to the orienting platform 76 similar to the outer set-up linkages via an additional first set-up linkage joints 84. Each of the set-up linkage extension links 102 is translatable relative to the associated set-up linkage base link 100 in a horizontal direction, which in many embodiments is aligned with the associated set-up linkage base link and the set-up linkage extension link 102. Each of the set-up linkage parallelogram linkage portions 104 configured and operable to selectively translate the set-up linkage vertical link 106 in a vertical direction while keeping the set-up linkage vertical link 106 vertically oriented. In example embodiments, each of the set-up linkage parallelogram linkage portions 104 includes a first parallelogram joint 112, a coupling link 114, and a second parallelogram 116. The first parallelogram joint 112 rotationally couples the coupling link 114 to the set-up linkage extension link 102. The second parallelogram joint 116 rotationally couples the set-up linkage vertical link 106 to the coupling link 114. The first parallelogram joint 112 is rotationally tied to the second parallelogram joint 116 such that rotation of the coupling link 114 relative to the set-up linkage extension link 102 is matched by a counteracting rotation of the set-up linkage vertical link 106 relative to the coupling link 114 so as to maintain the set-up linkage vertical link 106 vertically oriented while the set-up linkage vertical link 106 is selectively translated vertically. The second set-up linkage joint 108 is operable to selectively orient the manipulator support link 110 relative to the set-up linkage vertical link 106, thereby selectively orienting the associated attached manipulator 82 relative to the set-up linkage vertical link 106.

FIG. 7 is a perspective schematic representation of a robotic surgery system 120, in accordance with many embodiments. Because the surgery system 120 includes components similar to components of the surgery system 70 of FIG. 6, the same reference numbers are used for similar components and the corresponding description of the similar components set forth above is applicable to the surgery system 120 and is omitted here to avoid repetition. The surgery system 120 includes the mounting base 72, a support linkage 122, an orienting platform 124, a plurality of set-up linkages 126 (four shown), and a plurality of the surgical instrument manipulators 82. Each of the manipulators 82 is operable to selectively articulate a surgical instrument mounted to the manipulator 82 and insertable into a patient along an insertion axis. Each of the manipulators 82 is attached to and supported by one of the set-up linkages 126. Each of the set-up linkages 126 is rotationally coupled to and supported by the orienting platform 124 by the first set-up linkage joint 84. The orienting platform 124 is rotationally coupled to and supported by the support linkage 122. And the support linkage 122 is fixedly attached to and supported by the mounting base 72.

The support linkage 122 is operable to selectively position and/or orient the orienting platform 124 relative to the mounting base 72. The support linkage 122 includes the column base 86, the translatable column member 88, the shoulder joint 90, the boom base member 92, the boom first stage member 94, and the wrist joint 98. The support linkage 122 is operable to selectively set the distance between the shoulder joint 90 and the distal end of the boom first stage member 94. The wrist joint 98 rotationally couples the distal end of the boom first stage member 94 to the orienting platform 124. The wrist joint 98 is operable to selectively set the angular orientation of the orienting platform 124 relative to the mounting base 72.

Each of the set-up linkages 126 is operable to selectively position and/or orient the associated manipulator 82 relative to the orienting platform 124. Each of the set-up linkages 126 includes the set-up linkage base link 100, the set-up linkage extension link 102, the set-up linkage vertical link 106, the second set-up linkage joint 108, a tornado mechanism support link 128, and a tornado mechanism 130. Each of the set-up linkage base links 100 of the set-up linkages 126 can be selectively oriented relative to the orienting platform 124 via the operation of the associated first set-up linkage joint 84. Each of the set-up linkage vertical links 106 is selectively translatable in a vertical direction relative to the associated set-up linkage extension link 102. The second set-up linkage joint 108 is operable to selectively orient the tornado mechanism support link 128 relative to the set-up linkage vertical link 106

Each of the tornado mechanisms 130 includes a tornado joint 132, a coupling link 134, and a manipulator support 136. The coupling link 134 fixedly couples the manipulator support 136 to the tornado joint 132. The tornado joint 130 is operable to rotate the manipulator support 136 relative to the tornado mechanism support link 128 around a tornado axis 136. The tornado mechanism 128 is configured to position and orient the manipulator support 134 such that the remote center of manipulation (RC) of the manipulator 82 is intersected by the tornado axis 136. Accordingly, operation of the tornado joint 132 can be used to reorient the associated manipulator 82 relative to the patient without moving the associated remote center of manipulation (RC) relative to the patient.

FIG. 8 is a simplified representation of a robotic surgery system 140, in accordance with many embodiments, in conformance with the schematic representation of the robotic surgery system 120 of FIG. 7. Because the surgery system 140 conforms to the robotic surgery system 120 of FIG. 7, the same reference numbers are used for analogous components and the corresponding description of the analogous components set forth above is applicable to the surgery system 140 and is omitted here to avoid repetition.

The support linkage 122 is configured to selectively position and orient the orienting platform 124 relative to the mounting base 72 via relative movement between links of the support linkage 122 along multiple set-up structure axes. The translatable column member 88 is selectively repositionable relative to the column base 86 along a first set-up structure (SUS) axis 142, which is vertically oriented in many embodiments. The shoulder joint 90 is operable to selectively orient the boom base member 92 relative to the translatable column member 88 around a second SUS axis 144, which is vertically oriented in many embodiments. The boom first stage member 94 is selectively repositionable relative to the boom base member 92 along a third SUS axis 146, which is horizontally oriented in many embodiments. The wrist joint 98 is operable to selectively orient the orienting platform 124 relative to the boom first stage member 94 around a fourth SUS axis 148, which is vertically oriented in many embodiments.

Each of the set-up linkages 126 is configured to selectively position and orient the associated manipulator 82 relative to the orienting platform 124 via relative movement between links of the set-up linkage 126 along multiple set-up joint (SUJ) axes. Each of the first set-up linkage joint 84 is operable to selectively orient the associated set-up linkage base link 100 relative to the orienting platform 124 around a first SUJ axis 150, which in many embodiments is vertically oriented. Each of the set-up linkage extension links 102 can be selectively repositioned relative to the associated set-up linkage base link 10 along a second SUJ axis 152, which is horizontally oriented in many embodiments. Each of the set-up linkage vertical links 106 can be selectively repositioned relative to the associated set-up linkage extension link 102 along a third SUJ axis 154, which is vertically oriented in many embodiments. Each of the second set-up linkage joints 108 is operable to selectively orient the tornado mechanism support link 128 relative to the set-up linkage vertical link 106 around the third SUJ axis 154. Each of the tornado joints 132 is operable to rotate the associated manipulator 82 around the associated tornado axis 138.

FIG. 9 illustrates rotational orientation limits of the set-up linkages 126 relative to the orienting platform 124, in accordance with many embodiments. Each of the set-up linkages 126 is shown in a clockwise limit orientation relative to the orienting platform 124. A corresponding counter-clockwise limit orientation is represented by a mirror image of FIG. 9 relative to a vertically-oriented mirror plane. As illustrated, each of the two inner set-up linkages 126 can be oriented from 5 degrees from a vertical reference 156 in one direction to 75 degrees from the vertical reference 156 in the opposite direction. And as illustrated, each of the two outer set-up linkages can be oriented from 15 degrees to 95 degrees from the vertical reference 156 in a corresponding direction.

In use, it will often be desirable for a surgical assistant, surgeon, technical support, or other user to configure some or all of the linkages of robotic surgical system 140 for surgery, including the set-up structure linkage, the set-up joints, and/or each of the manipulators. Included among the task in configuring these linkages will be positioning the orienting platform 124 relative to first stage member 94 about vertical fourth SUS axis 148 of wrist joint 98. A joint drive motor 121 and/or brake system 123 is coupled to wrist joint 98, with one exemplary embodiment including both a drive 121 and brake 123. Additionally, a joint sensor system will typically sense an angular configuration or position of wrist joint 98.

An exemplary user interface, system, and method for manually configuring the system for use will be described herein with reference to manual articulation of orienting platform 124 by articulation of wrist joint 98 about fourth SUS axis 148, as schematically illustrated by arrow 127. It should be understood that alternative embodiments may be employed to articulate one or more alternative joints of the overall kinematic system, including one or more alternative joints of the set-up structure, one or more of the set-up joints, or one or more of the joints of the manipulators linkages. Use of the exemplary embodiment for articulating the motorized wrist joint embodiments may allow a user to efficiently position manipulators 82. The manual articulation of wrist joint 98 as described herein can improve speed and ease of use while manually docking manipulators 82 to their associated cannulas 64, as shown in FIG. 5B.

FIG. 10 shows a center of gravity diagram associated with a rotational limit of a support linkage for a robotic surgery system 160, in accordance with many embodiments. With components of the robotic surgery system 160 positioned and oriented to shift the center-of-gravity 162 of the robotic surgery system 160 to a maximum extent to one side relative to a support linkage 164 of the surgery system 160, a shoulder joint of the support linkage 164 can be configured to limit rotation of the support structure 164 around a set-up structure (SUS) shoulder-joint axis 166 to prevent exceeding a predetermined stability limit of the mounting base.

FIG. 11 schematically illustrates a method for positioning orienting platform 124 by articulating wrist joint 98. As generally described above, robotic system 140 may be used in a master following mode to treat tissues and the like. The robotic system will typically halt following, and will start 131 a configuration mode which allows a user to manually configure the orienting platform in a desired orientation about fourth SUS axis 148. Once the configuration mode has been entered, the current angle θ_(C) of wrist joint 98, as sensed by the joint sensor system, is set as the desired angle θ_(D) in step 133. If a cannula is mounted to any of the manipulators supported by platform 124, the system may apply the brake to the wrist joint and exit the configuration mode so as to inhibit manual movement of the wrist joint via step 135.

While in the configuration mode, when the platform is not moving about the wrist joint the system processor will typically transmit signals to the joint motor associated with wrist joint 98 so as to maintain the set desired angle θ_(D). Hence, when the system is bumped, pushed, or pulled lightly the wrist motor may urge the platform back toward the desired angle by applying a joint torque per an error E that varies with the difference between the sensed joint position and the desired joint position: E=θ−θ _(D) This driving of the joint toward the desired pose in step 137 will often be limited to allow a user to overcome the servoing of the wrist joint by applying sufficient effort 139 against the linkage system. For example, when the joint sensing system indicates a displacement of the joint beyond a threshold amount, when the torque being applied to the motor to counteract the applied force reaches a threshold amount, when a sensed force applied to the linkage system distally of the joint exceeds a threshold amount, or the like, the processor may halt servoing of the wrist joint to counteract articulation of the joint. In some embodiments there may be a time element of the effort threshold to overcome the servoing, such as by halting servoing in response to a torque that exceeds a threshold for a time that exceeds a threshold. Still other options are possible, including more complex relationships between the threshold force or torque and time, sensing that the force is applied to a particular linkage or subset of linkages supported by the wrist (or other articulatable joint), and the like. In an exemplary embodiment, a joint sensor between the orienting platform and the rest of the setup structure system provides a signal used to estimate torque applied to the orienting platform, and the joint displacement and servo stiffness are used to estimate a disturbance torque applied to the surgical arms and/or setup joints. In an additional exemplary embodiment, the error signal may be filtered so as to make the system more sensitive to transient pushes than slow or steady-state signals. Such error filtering may make the trigger more sensitive while limiting false triggers when the setup structure is on a sloped surface.

When a user pushes or pulls on one or more of the surgical manipulators, the set-up joint linkages, or directly on the platform with an effort sufficient to exceed the desired articulation threshold the user is able to rotate the orienting platform without having to fight the servo control. Although servoing so as to counteract the user movement of the platform is halted in step 141, drive signals may still be sent to the wrist motor. For example, friction compensation, gravity compensation, momentum compensation, and or the like may be provided 143 by applying appropriate drive signals during manual movement of the platform. Exemplary compensation drive systems are more fully described in US Patent Publication 2009/0326557 in the name of Neimeyer and entitled “Friction Compensation in a Minimally Invasive Surgical Apparatus,” in US Patent Publication 2011/0009880 in the name of Prisco et al. and entitled “Control System for Reducing Internally Generated Frictional and Inertial Resistance to Manual Positioning of a Surgical Manipulator,” and the like. In some embodiments, the system may employ joint range of motion limits alone or in addition to the drive signals when servoing is halted. Such range of motion limits may respond similar to servoing when a user pushes beyond a range motion limit except they are one sided.

Once the user has manually articulated the wrist near the desired orientation, the user will tend to slow the platform down and upon reaching the desired configuration will halt movement of the platform. The system takes advantage of this, and as the joint sensor indicates that movement of the platform falls below a desired threshold of zero the processor may, in response, re-set the desired joint angle and re-initiate servoing (or braking) so as to inhibit movement from that joint position. As the user may want to reverse direction of the manual joint articulation to correct any overshoot, the processor may not re-engage the servo until the articulation speed remains below a threshold for a desired dwell period.

Other variations are within the spirit of the present invention. Thus, while the invention is susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof are shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 

What is claimed is:
 1. A medical device comprising: a linkage having a joint; a drive unit coupled to the linkage; and a processor coupled with the drive unit, the processor being configured to: operate the medical device in a first state in which, in response to a first manual effort against the linkage below an articulation threshold, the processor transmits a first signal to the drive unit, the first signal causing the drive unit to inhibit manual articulation from a first pose of the linkage; operate the medical device in a second state in which, in response to a second manual effort against the linkage exceeding the articulation threshold, the processor transmits a second signal to the drive unit, the second signal causing the drive unit to facilitate a manual articulation from the first pose of the linkage toward a second pose of the linkage; and operate the medical device in a third state in which, in response to a determining that the linkage is at the second pose of the linkage, the processor transmits a third signal to the drive unit, the third signal causing the drive unit to inhibit manual articulation of the second pose of the linkage.
 2. The medical device of claim 1, further comprising: a joint sensor coupled to the joint, the joint sensor configured to sense a first torque applied by the first manual effort against the joint and transmit the first torque to the processor; the processor being configured to generate, in response to receiving the first torque, the first signal so that the first signal causes the drive unit to apply a counteracting torque to the joint that opposes the first torque and urges the linkage back toward the first pose of the linkage.
 3. The medical device of claim 2, the joint sensor configured to sense a second torque applied by the second manual effort against the joint and transmit the second torque to the processor, and the processor being configured to generate the second signal, in response to receiving the second torque and on condition that the second torque exceeds the articulation threshold, so that the drive unit decreases the counteracting torque so that the first torque is sufficient to manually move the linkage.
 4. The medical device of claim 3, wherein the processor is configured to determine the second manual effort exceeds the articulation threshold when the second torque exceeds a threshold torque.
 5. The medical device of claim 1, the second signal includes a friction compensation component that mitigates friction of the linkage during the manual articulation toward the second pose of the linkage.
 6. The medical device of claim 1, the processor being configured to determine that the linkage is at the second pose of the linkage on condition that a velocity of the manual articulation is below a threshold velocity.
 7. The medical device of claim 1, the processor being configured to determine that the linkage is at the second pose of the linkage on condition that a velocity of the manual articulation is below a threshold velocity for a threshold dwell time so that the drive unit facilitates a reversal of a direction of the manual articulation without inhibiting the manual articulation.
 8. The medical device of claim 1, the processor being configured to transmit the third signal to the drive unit to cause the drive unit to inhibit the manual articulation from the second pose of the linkage in response to a condition that a third manual effort against the linkage remains below the articulation threshold.
 9. The medical device of claim 1: wherein the linkage comprises a set-up structure having a proximal base and a platform, the joint being between the proximal base and the platform, wherein the platform supports a plurality of surgical manipulators, each manipulator comprising an instrument holder configured for releasably receiving a surgical instrument, and wherein the manual articulation from the first pose to the second pose alters positions of the plurality of surgical manipulators relative to a surgical site.
 10. The medical device of claim 1, the linkage being included in a surgical manipulator having an instrument holder and a cannula interface, the instrument holder being configured for releasably receiving a surgical instrument, and the cannula interface being configured for releasably receiving a cannula, the surgical manipulator being configured to pivotably move a shaft of the surgical instrument within a minimally invasive surgical aperture adjacent the cannula so as to manipulate an end effector of the surgical instrument, and the processor being configured to operate the medical device in a fourth state in which, in response to the cannula being mounted to the cannula interface, the processor transmits a fourth signal to the drive unit, the fourth signal causing the drive unit to inhibit manual articulation of the joint by a third manual effort against the linkage exceeding the articulation threshold.
 11. The medical device of claim 1, wherein the drive unit comprises a brake, and wherein causing the drive unit to inhibit manual articulation comprises causing an application of the brake.
 12. The medical device of claim 1, wherein the articulation threshold comprises a torque.
 13. The medical device of claim 1, wherein the articulation threshold comprises a force.
 14. A surgical system comprising: a linkage comprising a joint between a proximal base and an instrument holder configured for releasably supporting a surgical instrument; a drive system coupled to the linkage; a torque sensor system coupled to the joint; and a processor coupling the torque sensor system with the drive system, the processor configured to: operate the surgical system in a first state in which, in response to a first torque sensed by the torque sensor system being below an articulation torque threshold, the processor transmits a first drive signal to the drive system, the first drive signal causing the drive system to inhibit manual articulation from a first joint configuration; operate the surgical system in a second state in which, in response to a second torque sensed by the torque sensor system exceeding the articulation torque threshold, the processor transmits a second drive signal to the drive system, the second drive signal causing the drive system to facilitate a manual articulation from the first joint configuration toward a second joint configuration using a movement torque lower than the articulation torque threshold; and operate the surgical system in a third state where, in response to a determination that the linkage is at the second joint configuration on condition that a velocity of the manual articulation being below a threshold velocity, the processor transmits a third drive signal to the drive system, the third drive signal causing the drive system to inhibit manual articulation from the second joint configuration on condition that a third torque sensed by the torque sensor system being below the articulation torque threshold.
 15. A method comprising: operating a medical device comprising a linkage having a joint, a drive unit coupled to the linkage, and a processor coupled to the drive unit in a first state in which, in response to a first manual effort against the linkage below an articulation threshold, the processor transmits a first signal to the drive unit, the first signal causing the drive unit to inhibit manual articulation from a first pose of the linkage; operating the medical device in a second state in which, in response to a second manual effort against the linkage exceeding the articulation threshold, the processor transmits a second signal to the drive unit, the second signal causing the drive unit to facilitate a manual articulation from the first pose of the linkage toward a second pose of the linkage; and operating the medical device in a third state in which, in response to a determining that the linkage is at the second pose of the linkage, the processor transmits a third signal to the drive unit, the third signal causing the drive unit to inhibit manual articulation of the second pose of the linkage.
 16. The method of claim 15, further comprising: sensing, using a joint sensor coupled to the joint, a first torque applied by the first manual effort against the joint; and generating, in response to receiving the first torque, the first signal so that the first signal causes the drive unit to apply a counteracting torque to the joint that opposes the first torque and urges the linkage back toward the first pose of the linkage.
 17. The method of claim 16, sensing, using the joint sensor, a second torque applied by the second manual effort against the joint; and generating the second signal, in response to receiving the second torque and on condition that the second torque exceeds the articulation threshold, so that the drive unit decreases the counteracting torque so that the first torque is sufficient to manually move the linkage.
 18. The method of claim 17, further comprising determining the second manual effort exceeds the articulation threshold when the second torque exceeds a threshold torque.
 19. The method of claim 15, further comprising generating the second signal to include a friction compensation component that mitigates friction of the linkage during the manual articulation toward the second pose of the linkage.
 20. The method of claim 15, further comprising determining that the linkage is at the second pose of the linkage on condition that a velocity of the manual articulation is below a threshold velocity.
 21. The method of claim 15, further comprising determining that the linkage is at the second pose of the linkage on condition that a velocity of the manual articulation is below a threshold velocity for a threshold dwell time so that the drive unit facilitates a reversal of a direction of the manual articulation without inhibiting the manual articulation.
 22. The method of claim 15, further comprising transmitting the third signal to the drive unit to cause the drive unit to inhibit the manual articulation from the second pose of the linkage in response to a condition that a third manual effort against the linkage remains below the articulation threshold.
 23. The method of claim 15, further comprising causing the drive unit to inhibit manual articulation by applying a brake of the drive unit.
 24. The method of claim 15, wherein the articulation threshold comprises a torque.
 25. The method of claim 15, wherein the articulation threshold comprises a force. 